The update-by-query API is new and should still be considered experimental. The API may change in ways that are not backwards compatible

The simplest usage of _update_by_query just performs an update on every
document in the index without changing the source. This is useful to
pick up a new property or some other online
mapping change. Here is the API:

_update_by_query gets a snapshot of the index when it starts and indexes what
it finds using internal versioning. That means that you’ll get a version
conflict if the document changes between the time when the snapshot was taken
and when the index request is processed. When the versions match the document
is updated and the version number is incremented.

All update and query failures cause the _update_by_query to abort and are
returned in the failures of the response. The updates that have been
performed still stick. In other words, the process is not rolled back, only
aborted. While the first failure causes the abort all failures that are
returned by the failing bulk request are returned in the failures element so
it’s possible for there to be quite a few.

If you want to simply count version conflicts not cause the _update_by_query
to abort you can set conflicts=proceed on the url or "conflicts": "proceed"
in the request body. The first example does this because it is just trying to
pick up an online mapping change and a version conflict simply means that the
conflicting document was updated between the start of the _update_by_query
and the time when it attempted to update the document. This is fine because
that update will have picked up the online mapping update.

Back to the API format, you can limit _update_by_query to a single type. This
will only update tweet`s from the `twitter index:

POST /twitter/tweet/_update_by_query?conflicts=proceed

You can also limit _update_by_query using the
Query DSL. This will update all documents from the
twitter index for the user kimchy:

The query must be passed as a value to the query key, in the same
way as the Search API. You can also use the q
parameter in the same way as the search api.

So far we’ve only been updating documents without changing their source. That
is genuinely useful for things like
picking up new properties but it’s only half the
fun. _update_by_query supports a script object to update the document. This
will increment the likes field on all of kimchy’s tweets:

Just as in Update API you can set ctx.op = "noop" if
your script decides that it doesn’t have to make any changes. That will cause
_update_by_query to omit that document from its updates. Setting ctx.op to
anything else is an error. If you want to delete by a query you can use the
Delete by Query plugin instead. Setting any
other field in ctx is an error.

Note that we stopped specifying conflicts=proceed. In this case we want a
version conflict to abort the process so we can handle the failure.

This API doesn’t allow you to move the documents it touches, just modify their
source. This is intentional! We’ve made no provisions for removing the document
from its original location.

It’s also possible to do this whole thing on multiple indexes and multiple
types at once, just like the search API:

POST /twitter,blog/tweet,post/_update_by_query

If you provide routing then the routing is copied to the scroll query,
limiting the process to the shards that match that routing value:

POST /twitter/_update_by_query?routing=1

By default _update_by_query uses scroll batches of 100. You can change the
batch size with the scroll_size URL parameter:

In addition to the standard parameters like pretty, the Update By Query API
also supports refresh, wait_for_completion, consistency, and timeout.

Sending the refresh will update all shards in the index being updated when
the request completes. This is different than the Index API’s refresh
parameter which causes just the shard that received the new data to be indexed.

If the request contains wait_for_completion=false then Elasticsearch will
perform some preflight checks, launch the request, and then return a task
which can be used with Tasks APIs to cancel
or get the status of the task. For now, once the request is finished the task
is gone and the only place to look for the ultimate result of the task is in
the Elasticsearch log file. This will be fixed soon.

consistency controls how many copies of a shard must respond to each write
request. timeout controls how long each write request waits for unavailable
shards to become available. Both work exactly how they work in the
Bulk API.

timeout controls how long each batch waits for the target shard to become

this object contains the actual status. It is just like the response json
with the important addition of the total field. total is the total number
of operations that the reindex expects to perform. You can estimate the
progress by adding the updated, created, and deleted fields. The request
will finish when their sum is equal to the total field.